The present invention is to provide metal powder capable of decomposing and remedying various range of organic halogen compounds including organic halogen compounds which are difficult to be decomposed by a conventional decomposition and remediation method. Metal powder for decomposition of organic halogen is prepared in such a manner that the metal powder contains at least two kinds or more of metal elements, the respective metal elements forming phases, the respective metal elements therein serving as major constituents thereof, wherein difference in standard oxidation-reduction electric potential between any two kinds among the above-described metal elements is 778 mV or more in absolute value. When remediation treatment of soil is carried out using the metal powder, it is sufficient that the metal powder for decomposition of organic halogen is mixed with agitation into soil using, for instance, a heavy machine, and when remediation treatment of ground water, it is sufficient that a reaction wall containing the metal powder for decomposition of organic halogen into is constructed in the ground.